The findings are the first to show that carbon dioxide makes fish in the wild act just as crazy as fish dosed with the greenhouse gas in the lab, says marine biologist Astrid Wittmann of the Alfred Wegener Institute in Bremerhaven, Germany, who was not involved with the new work.

As carbon dioxide pours into the atmosphere, the gas filters down into oceans, slowly but steadily dialing up the waters’ acidity. In laboratory tests, fish exposed to carbon dioxide–infused waters have hearing and learning problems and odd behavior issues: They seek out predators’

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